The overall goal of our research program is to build a comprehensive theoretical understanding of human auditory processing by utilizing advanced spatiotemporal brain imaging methods combining fMRI, MEG, and EEG. During the first funding cycle, we used spatiotemporal imaging to investigate the role of transient adaptation of feature-specific neurons in auditory sensory memory and pre-attentive sound novelty detection. We will continue to investigate these mechanisms of early auditory processing to explain how the brain represents temporally distributed sound signals (Aim 1). Furthermore, our new perspective expands the scope of the investigation from these lower-level mechanisms to dynamic modulations from extra-acoustic influences including top-down modulation of selective attention (Aim 2) and multisensory inputs (Aim 3), which play important roles in adaptively re-shaping neuronal activity based on the current behavioral context. In addition, we will continue to develop novel experimental paradigms and spatiotemporal brain imaging methods, to achieve more accurate and sensitive non-invasive tools for investigating the functional organization of the human auditory system. The major significance of this proposal is that the work it proposes will provide a better understanding of the neural mechanisms responsible of auditory processing in the human brain: Although a series of successful animal studies have led to the development of several competing hypotheses, a paucity of information exists about the physiological mechanisms that allow us to grasp the vast amount of information embedded within our everyday acoustic environment. Our proposed comprehensive spectral and spatial analysis of human brain activity will reveal the collection of brain regions involved in auditory processing as well as the sequence of their causal interactions. The empirical information on structure/function relationship in auditory cortex can be incorporated into computational models of human auditory processing. Furthermore, our spatiotemporal brain imaging techniques may provide significant advantages in the investigation of clinical disorders with abnormal auditory perceptual functions. PUBLIC HEALTH RELEVANCE This research program uses an advanced combination of brain imaging methods to investigate how the human brain processes auditory information. In addition to providing information on neuronal mechanisms on auditory sensory memory, selective attention, and visual influence on speech perception, our techniques may provide significant advantages in the investigation of a variety disorders with abnormal auditory perceptual functions, such as schizophrenia. Our scientific results may also help develop speech-detection algorithms as well as techniques for hearing aids and prosthetics.